The fender / wheel arch extension serves to cover the wheels of a vehicle in sufficient form so as not to endanger other road users, in particular pedestrians, by the rotational movement of a freestanding wheel. According to German motor vehicle law (§ 36a StVZO) wheels must not protrude from the body or have a cover for this reason. Similar provisions exist in other countries. Likewise, mudguards / wheel arch extensions prevent unnecessarily large turbulence of water from the road surface, which could hinder the following road users in the view. This would occur in freestanding wheels in extreme form.